The present invention relates generally to an apparatus for delivering water to an internal combustion engine and more specifically to a delivery tube assembly for providing cooling water between a power pack and a cooling manifold of a diesel-electric locomotive.
In the art relating to internal combustion engines, it is well known to provide piston cylinders having hollow interior portions that are cooled from a source of water supplied by various pipes and tubes. For example, heavy duty engines in locomotives are typically diesel engines that are used to generate electricity that power the electric motors, which electric motors provide the electromotive force to the wheels. Such diesel engines are water cooled, where water from a cooling manifold is supplied by rigid metal pipe to each xe2x80x9cpower packxe2x80x9d of the diesel engine. Each power pack contains a single cylinder and associated mechanicals and mounting structure, and a typical locomotive diesel engine may include sixteen such power packs for a xe2x80x9csixteen cylinderxe2x80x9d engine. Accordingly, a sixteen cylinder engine would have sixteen metal cooling pipes connected to the manifold. Of course, such engines may have eight, twelve, sixteen or twenty cylinders, as is known in the art.
In a particular model of locomotive, the position of the power pack with respect to the manifold pipe is fixed within certain dimensional tolerances. Accordingly, the cooling pipe must have a specific configuration with respect to bends, its length, and the like, in order to be able to fit and connect between the power pack and the cooling manifold.
Such rigid metal pipes have been used for many years in locomotive applications. These known pipes have a curved portion and welded or brazed flanges at each end. The curve is required due to the relative positions of the outlet and inlet apertures on the manifold and the power pack, respectively and the distance separating the apertures. The flange securing the cooling pipe to the power pack is secured using two bolts, while the flange securing the cooling pipe to the manifold is typically secured using two U-shaped bolts, where the ends of each U-shaped bolt are threaded and are received through a pair of bolt holes in the flange and secured by corresponding nuts.
However, several problems are caused by the use of a rigid pipe. First, locomotive engines are not necessarily made to precision tolerances with respect to the position between the power pack and the manifold. When the flange bolts are tightened, the manifold may move slightly to permit a tight seal to be made between the flanges and the power pack and manifold, respectively. As the flange bolts are tightened, if any misalignment exists, the rigid cooling pipe and flange are stressed. The greater the misalignment or dimensional tolerance between power pack and the manifold, the greater the stress applied to the cooling pipe.
Further, as described above, several such rigid cooling pipes may be used, which are typically disposed along the manifold at equal intervals, depending of course, on the number of power packs in the engine. Because the manifold is essentially a long tube, it is secured at its ends, and may have supports along its length. Accordingly, the manifold is able to flex a certain amount.
Additionally, because the manifold is fixed at its ends, it may be able to flex more toward its midsection than it can at its endpoints or attachment mounting, where it is fixed. In some locomotive configurations, for example, for cooling pipes disposed toward the middle of the manifold, tightening the bolts on the flanges, while subjecting the cooling pipe and flange to stress, may only induce moderate stress, depending upon the misalignment between the manifold and the power pack for that particular engine. However, for cooling pipes disposed toward the ends of the manifold, the manifold is very stiff and does not easily move. When the flange bolts are tightened for such end-located cooling pipes, the rigid pipe and flange may be subject to much greater stress and torque. This may cause metal fatigue and stress fractures resulting in the destruction of the cooling pipe, necessitating repair and replacement prior to the normal lifetime of the cooling pipes.
Moreover, such locomotive diesel engines are large heavy-duty engines and generate significant amounts of vibration when in operation. Accordingly, there is significant vibratory motion between the components of the engine. This induces further stress in the rigid cooling pipe as the manifold and the power pack vibrate relative to each other, and such stress further reduces the normal lifetime of the cooling pipe.
Various attempts have been made to overcome the aforementioned shortcomings of rigid cooling pipes. One known attempt to overcome such problems is to replace the curved rigid cooling pipe with a curved flexible cooling pipe. Again, the curve is required to permit the cooling pipe to fit between the power pack and the manifold. Accordingly, it is known to replace the rigid pipe with a corrugated pipe made from, for example, thin-wall stainless steel. Corrugating the stainless steel pipe increases its flexibility and permits it to bend to some degree. To meet required structural integrity and strength requirements, the corrugated pipe is covered with a stainless steel wire braid. The braid typically increases the bursting strength of the pipe.
Although this known configuration using a corrugated stainless steel pipe and associated braid was an improvement over the rigid cooling pipe, it was found that the harsh operating environment of the locomotive engine, and in particular, the constant and significant vibration, causes the braid to rub or chafe against the underlying corrugated pipe. Over time, such chafing abraded the metal surface of the corrugated pipe until the corrugated pipe was breached. When this occurs, a leak develops, again necessitating replacement of the cooling pipe and removal of the locomotive from service for unscheduled maintenance. Surprisingly, the braid was found to breach the corrugated pipe in a short period of operation, significantly less than the expected lifetime of the cooling pipe. Again, this is relatively costly, not only from the point of view of replacement parts, but significantly, due to the operational cost associated with removing the locomotive from service for repair and premature maintenance.
Additionally, because the corrugated pipe was bent at an angle to accommodate attachment of the flanges to the power pack and manifold, respectively, the tight bend essentially rendered the corrugation very stiff at the xe2x80x9celbow,xe2x80x9d to a point where it behaves like a solid pipe. The braid is essentially xe2x80x9cstretchedxe2x80x9d around the bend or elbow of the corrugated pipe, causing the braid to rub with even greater force against the corrugated pipe, especially at the outside bend of the corrugated pipe. This, in part, additionally contributed to the reduced lifetime of the corrugated pipe.
Another known configuration again uses a corrugated metal pipe with metal braid, which configuration is also curved. However, this configuration includes a Teflon liner inside the corrugated metal pipe, presumably to smooth out the fluid flow. Because a Teflon liner is used, the pipe cannot be welded or brazed, or otherwise be subject to high heat processing. The corrugated pipe and metal braid are therefore crimped into the flanges or housings to form the assembly. However, the crimp is adversely affected by the high levels of vibration, and fail prematurely. Thus, this known configuration is also unacceptable.
A need exists for a cooling pipe assemble for use in a locomotive diesel engine that can withstand the harsh operating environment and provide adequate lifetime.
The disadvantages of present cooling water delivery systems may be substantially overcome by providing a novel cooling water delivery assembly. More specifically, in one embodiment, a water delivery tube assembly for use in an internal combustion engine of a locomotive provides water between an inlet aperture of a power pack and an outlet aperture of a manifold, where the inlet aperture and outlet aperture are longitudinally offset from each other and are disposed in misaligned planes. The assembly includes a flexible metal pipe having inlet and outlet ends, and a metal braid surrounding the pipe. Inlet and outlet housings are operatively coupled to the inlet and outlet ends of the pipe, respectively and defme an internal fluid flow path in fluid communication with the pipe. The inlet and outlet housings have compound angles defining the fluid flow path such that when the inlet housing is secured to the power pack and the outlet housing is secured to the manifold, the flexible metal pipe is maintained in a substantially linear configuration between the housings.